Characterizing Gas-Particle Interactions of Phthalate Plasticizer Emitted from Vinyl Flooring

Phthalates are widely used as plasticizers, and improved ability to predict emissions of phthalates is of interest because of concern about their health effects. An experimental chamber was used to measure emissions of di-2-ethylhexyl-phthalate (DEHP) from vinyl flooring, with ammonium sulfate particles introduced to examine their influence on the emission rate and to measure the partitioning of DEHP onto airborne particles. When particles were introduced to the chamber at concentrations of 100 to 245 mu g/m(3), the total (gas + particle) DEHP concentrations increased by a factor of 3 to 8; under these conditions, emissions were significantly enhanced compared to the condition without particles. The measured DEHP partition coefficient to ammonium sulfate particles with a median diameter of 45 +/- 5 nm was 0.032 +/- 0.003 m(3)/mu g (95% confidence interval). The DEHP-particle sorption equilibration time was demonstrated to be less than 1 min. Both the partition coefficient and equilibration time agree well with predictions from the literature. This study represents the first known measurements of the particle-gas partition coefficient for DEHP. Furthermore, the results demonstrate that the emission rate of DEHP is substantially enhanced in the presence of particles. The particles rapidly sorb DEHP from the gas phase, allowing more to be emitted from the source, and also appear to enhance the convective mass-transfer coefficient itself. Airborne particles can influence SVOC fate and transport in the indoor environment, and these mechanisms must be considered in evaluating exposure and human health.